The Lumbar Spine and Lower Extremity

The Lumbar Spine and Pelvis in Kinesiology

Anatomy of the Lumbar Spine

  • Lumbar Vertebrae: 5 Vertebrae

    • Natural Lordosis: The lumbar spine has a natural lordotic curve.

    • Increasing Size: The vertebrae grow in size from L1 to L5 to facilitate connection with the sacrum at the LumboSacral Joint.

    • Anomalies: There is a higher opportunity for anomalies due to a lack of fusion.

    • Weight Bearing Tolerance: The lumbar spine has a much higher tolerance for weight-bearing and compressive loads due to its structure.

  • Sacrum:

    • Structure: Strong, triangular bone located between the two innominate bones, forming the Sacroiliac Joint.

  • Coccyx:

    • Comprised of 4 fused vertebrae.

    • Serves as an attachment site for ligaments and muscles.

Spinal Structure

Key Structures:

  • Spinous Process

  • Superior Articular Facet

  • Supraspinous Ligament

  • Interspinous Ligament

  • Superior Articular Process

  • Transverse Process

  • Ligamentum Flavum

  • Posterior Longitudinal Ligament

  • Dura Mater

  • Annulus Fibrosus

  • Nucleus Pulposus

  • Anterior Longitudinal Ligament

Spinal Cord and Peripheral Nerves

  • Spinal Cord: Ends around L1, transitioning into the Cauda Equina, which is described as a whiplike "horse’s tail".

  • Spinal Nerves: Continue on exiting at each vertebral level, supplying sensory and motor neurons to the lower extremity, pelvic floor muscles, and organs.

Innervation Details:

Cervical Nerves

  • C1: Head and neck

  • C2: Diaphragm

  • C3: Deltoids, Biceps

  • C4:

  • C5: Wrist Extenders

  • C6: Triceps

  • C7: Hand

  • T1 - T2: Thoracic nerves

Thoracic and Lumbar Nerves

  • T5 - T8: Control of chest and abdominal muscles

  • L1-L2: Segmental innervation of hip flexors, adductors

  • L3 - L5: Leg muscles

  • S1: Bowel and bladder control

  • S2-S4: Sexual function

Joint Mechanics of the Lumbar Spine

  • Movement in Sagittal Plane: The lumbar spine primarily moves in the sagittal plane.

  • Lumbar Rotation:

    • Components: Involves the superior and inferior vertebra, joint capsule, and ligaments.

Key Muscle Groups

  1. Deep Back Muscles:

    • Semispinalis Dorsi

    • Multifidus

    • Longissimus Capitis

    • Iliocostalis Cervicis and Dorsi

    • Spinalis Dorsi

  2. Abdominal Muscles:

    • Transversus Abdominis: Provides stabilization to lumbar spine

    • Rectus Abdominis: Responsible for trunk flexion and is essential in maintaining pelvic alignment.

  3. Quadratus Lumborum:

    • Works as a stabilizer for the lumbar spine and assists lateral flexion.

Thoracolumbar Fascia

  • Description: A dense connective tissue structure starting at the lower thoracic spine and connecting with the sacrum and iliac crest.

  • Function: This fascia serves as an attachment site for various muscle groups, including the Lats and Glutes, aiding in stabilizing the spine and transmitting forces between the spine and lower extremities.

Anatomy of the Pelvis

  • Innominate Bones: Comprised of the left and right bones with three fused components: Ilium, Ischium, and Pubis.

  • Ilium:

    • Wide structure with prominent iliac crests, including key landmarks: Anterior Superior Iliac Spine (ASIS) and Posterior Superior Iliac Spine (PSIS).

  • Ischium:

    • Contains Ischial Tuberosity and other key structures.

  • Pubis:

    • Comprises the pubic symphysis, allowing minimal movement.

Female Pelvis vs. Male Pelvis

  • Differences: The female pelvis is generally wider, flatter, and tilted more forward to accommodate childbirth.

Movements of the Pelvis

  • Pelvic Tilting: Can undergo anterior, posterior, and lateral tilting, as well as rotational movements.

Sacroiliac Joint (SI Joint)

  • Location and Palpation: Palpable at PSIS.

  • Dysfunction Causes: Ligament laxity, tight musculature, skeletal dysfunction, malalignment, trauma, and degeneration can lead to dysfunction in the SI joint.

Functionality of Muscles in the Pelvis and Lower Spinal Region

  • Iliopsoas: Acts primarily in hip flexion during both non-weight bearing and weight-bearing situations.

  • Gluteus Maximus: Functions in hip extension and external rotation, assisting in hip abduction.

  • Hip Stabilization: Essential for coordinated movement of the lower extremities.

Bursitis and Related Conditions

  • Types of Bursae:

    • Ischial bursa

    • Deep and Superficial Trochanteric Bursae

    • Iliopsoas bursa

Gait Cycle

Rancho Los Amigos Terminology

  • Divides the gait cycle into Stance Phase (62%) and Swing Phase (38%)

  • Stance Phase Subdivisions:

    • Loading Response

    • Midstance

    • Terminal Stance

  • Swing Phase Subdivisions:

    • Pre-Swing

    • Initial Swing

    • Mid Swing

    • Terminal Swing

Muscle Activity During Gait

  • Iliopsoas Activity: Inactive throughout most phases except concentric during swing.

  • Gluteus Maximus Functions: Eccentric during loading and controlled movements.

  • Hamstrings and Quadriceps Contributions: Eccentric during stance and concentric during swing phases.

Conclusion

  • Importance of Muscle Strength: Weakness in proximal musculature, particularly the gluteus medius and maximus, contributes significantly to movement impairments and orthopedic injuries in the knee.

References:

  • MacAskill MJ, et al. Research on gluteal muscle activity.

  • Physiopedia, Discussion on TFL and its functional role in gait.